Method of producing wood pulp



Aug. 2, 1960 l.. E. EBERHARDT 2,947,655

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Les E. Enna/MDT 2,947,655 METHOD F PRODUCING WGOD PULP Lee E. Eberhardt,Springield, Ohio, assignor to The Bauer Bros. Company, Springfield,Ohio, a corporation of hio Filed Apr. 21, 1955, Ser. No. 502,980

13 Claims. (Cl. 162-26) This invention relates to the production of woodpulp and more particularly to the apparatus and method for producing awood pulp comparable to groundwood.

Groundwood pulp is now produced by grinding or abrading barked logs. Inpractice the wood is generally cut in four foot lengths, the barkremoved therefrom and sorted as to straight and crooked wood. Crookedwood, for example, branches, deformed limbs, and the like, is notsuitable for the production of groundwood bythe normal process since itcannot be eiectively or satisfactorily held in contact engagement withthe face of the abrading or grinding wheel. The grinder is generally arelatively large machine having an abrasive stone with a four foot wideperipheral face, against which the logs are placed with their taxesparallel to the axis of the stone. The logs, when held under pressure incontact with the moving face of the stone, are abraded to therebyproduce a collection of fibers.

It has been found that a pulp comparable in quality to groundwood can beproduced by making chips of the raw wood, passing these chips through arotary press in which pressure is successively applied and removedduring travel of the chips through the press, and then completing theiiberizing of the chips material in a disc mill or rener. The quality ofthe pulp so produced is equal to, or in some instances better than, thatproduced by the conventional method and such pulp is produced at aconsiderablesavings in power requirements.V

A further advantage of the process is that it permits the use of smalldiameter wood, crooked wood, slabs, edgings, and other forms of woodwhich are either impossible or impractical to use inthe conventionalprocessing of groundwood. t

The present invention involves not only a new process for themanufacture of pulp comparable to groundwood but the discovery of theadaptability and usefulness Vof conventional equipment for theproduction of a groundvvood type pulp. The equipment used in the presentprocess for the production of groundwood type pulp is entirelyrdifferent than any that has heretofore been used for this purpose. Itis nevertheless `standard equipment in Ithat it -is well known for otherapplications. When used in accordance with the present process anentirely new and unexpected result is obtained. Considerable advantage`is gained over the conventional methods and apparatus for producinggroundwood pulp.` Such advantage is three-fold, namely, first, use ofconventional equipment eliminates the necessity for speciality equipmentsuch as the grinding wheel and its associated equipment, second,considerable less -power is required, and third, scrap wood and othertypes of wood heretofore unusable for production of 4groundwood are nowmade usable. p

Thus, the object of the invention is to improve the con struction aswell as the means and method of operation offgroundwood pulp mills asdisclosed herein, whereby such groundwood pulp may not only be moreeconomically manufactured but will provide more eificient utilization ofpower and wood supply.

A further object of the invention is to provide means wherebymultipurpose equipment can be used for the manufacture of groundwoodpulp.

A further object of the invention is to provide a new process by meansof which groundwood pulp can be made with conventional equipment.

A further object of the invention is to provide a means and a processfor producing groundwood pulp which will provide more efficientutilization of the raw wood material from which the groundwood pulp i-smade.

A further object of the invention is to provide a means and a processfor producing groundwood pulp with less power consumption than is nownormal.

A further object of the invention is to provide a means and a processwhereby a complete utilization of the raw material may be achieved.

A further object of the invention is to provide a means and process forproducing groundwood pulp wherein waste or lost material is relativelysmall.

A further object of the invention is to provide a means and process forthe production of groundwood pulp which will produce desirableby-products in a form which can be utilized.

A further object of the invention is to provide a means and process forproducing groundwood type pulp posssing the advantageous features, theinherent meritorious characteristics and the mode of operation hereindescribed.

With the above primary and other incidental objects in view as will morefully appear in this speciiication, the invention intended to beprotected by Letters Patent consists of the features, the parts andcombinations thereof, and the mode of operation and process ashereinafter described or illustrated in the accompanying drawing, ortheir equivalents.

Referring to the accompanying drawing wherein is shown ilow diagrams ofthe preferred but obviously not necessarily the only forms ofembodimentV of the invention:

Fig. 1 is a diagrammatic ilow chart of one form of the invention;

Fig. 2 is a flow chart similar to Fig. 1, but having one step in theprocess eliminated;

Fig. 3 is a portion of the chart shown in' Figs. 1 and 2 with a reversalin sequence of two of the steps;

Fig. 4 is 4a portion of the ow chart of Figs. 1 and 2 showing anoptional return of rejects, which may be incorporated in the charts ofFigs. l and 2 or the modication of Fig. 3; and

Fig. 5 is a diagrammatic flow chart of a further modication of theprocess shown in Fig. l.

Like parts are indicated by similar characters of reference throughoutthe several views.

Referring to the drawings there is shown in Fig. 1 a ow diagram for thetypical installation incorporating the present process for theproduction of groundwood type pulp. The raw wood, wood waste, edgings,slabs and the like are fed to a chipper 1 wherein the raw wood ofwhatever type, is chipped or' broken into relatively small pieces. Suchcln'p'pers,- although possibly varying to some extent in detailconstruction, all operate on the same principle. The raw wood isadvanced to a cutting mechanism which in effect slices from the end ofthe log, slab, or the like a thin slice. This slice as it falls bygravity breaks into small 'chips or pieces. These chipsor pieces arethen collected for further processing.

The chips are taken from the chipper and placed in a soaking vat wheremoisture is reintroduced Vinto the chips and all chips are brought to acommon level of moisture content. Depending upon the typeof chips 3being processed, the inclusion in this soaking vat of a wetting agent ora weak chemical solution such as a weak solution of sodium hydroxide orother softening agents. may bedesirable.

This soaking or wetting step is not necessary in all instances.. It is,however, desirable when the wood being processed is veneer or kiln driedlumber waste which wood is extremely dry. The iiow diagram for theprocess without the inclusion of the wettingstep isshown in Fig. 2.

The chips are then taken `from the wetting vat at a uniform level ofmoisture,` and placed in a rotary press .'1.V In the event the soakingstep Vis omitted (Fig. 2) thechips-as they come from the chipper are ata substantially uniform moisture level and can-be fully'- and properlyprocessed in the press 3 the same as if they had undergone the wettingstep. The rotary press 3 is of a screw type similar to that which hasbeen heretofore used in the oil industry for extraction of oil fromcotton seed,- tungnutsl and the like. The particular press used hereininvolves a succession of pressure applications and releases duringtravel of the wood material through the press. The material beingprocessed is compressed by the rotation of a helical'feed screw andgradually advanced through a restricted area. As the material passes therestricted area itis permitted to expand where pressure is released.l Aspressure is released the feed screw again picks up the material andagain presses or applies pressure thereto in the advancement of thematerial past a further restricted area. During thepressing of the woodit is subjected not only to pressure but also to a twisting or shearingaction due to the rotary motion of the feed screw. The material withinthe press is therefor subjected simultaneously to a squeezing andshearing action and to the successive application and release ofrelatively high pressures. Such treatment ofthe material extractsVtherefrom the greater part of the moisture and in addition thereto someofthe natural wood uids such as'sap, rosin, and chemicals normallypresent in the wood. The lignin and other wood sugars areV also softenedduring this pressing operation.

During such extraction of these materials a certain degreefofheat isdeveloped in the press which materially assists in the processing of thewood and the satisfactory extraction of these other compounds. The heatdeveloped, however, is not comparable to that of the normal cookingoperation as is generally used in theprocessing'of bers for pulppurposes.

The material extracted from the wood chips during the pressingoperation' may be later separatedor classied and subsequently disposedof as by-products of the present process.

The rotary press causes a breakdown-of the chipped material and anopening up of the iiberous structure thereof.. A high degree ofiberizing, maceration or brillation is achieved by the successiveapplication and release of pressure combined with the squeezing andshearing produced by the rotary screw member. The material, as it isdischarged from the press, is in excellent condition for furtherrefining or treatment to produce a ground wood type of pulp byconventional attrition means.

AsV the partially berized chips are discharged from lrotary'press thefibers thereof are immediately rewet or moistened either with water or.a vapor so as to prevent damage thereto during handling. It ispreferable that some wetting or moistening of the material take place atthe point of inal pressure release in therotary press since at: thispoint the material is eXtreme receptive to the introduction of themoisture and will readily absorp it.

The moistened material is then transferred to a conventional attritionmill. During such transfer, additional waterV is added thereto so as toproduce a mixture suitablefor further refining in the attrition mill.

The attrition mill 4 is preferably of the disc type and maybeof anyconventional design, `i.e. a singleI disc lmillV or a double disc mill.The partially tiberized material is subjected to a high degree offiberizing action in the attrition mill which produces a long ibrousmaterial generally similar in overall quality to that normally used ininsulation board material. However, mixed in with the long hers arenumerous short length fibers and also probably some long shives. Shi'vesare groups of fibers which have not beenfully Aseparated-by theYprocessing to this point.

The material as it comes-from -attrition mill-.4 is then The output ofthe second `stage renner 5 'is of the type commonly used in newsprint,lower quality book papers and the like, and constitutes a pulp which isin quality equal to or better than the Yuormallyprduced ground woodpulp.

The pulp as. it is discharged from'thesecondretining.

stage -is introduced into a centrifugal cleanerl 6. The cleaner 6Veffects a substantiallycornplete removal of dirt, bark specks, shortstubby iibers or shor-t and stubbyshives. Also removed by thecentrifugal cleaner are all inorganic or Vforeign organic materialsvwhich would reduce .thepulp quality. The material rejected by-thecentrifugal cleaner 6 is discharged to waste, as--shown in Fig-1, whilethe material accepted or passed by the centrifugal cleaner is conveyedtoarotary` screen 7.

The rotary screen grades the pulp,- ,separatingtherefrom-v as rejectsany long shives, clusters ofunseparated fibersv and the like.- Suchmaterial as is rejected by the rotary screen 7 is returned to the rotarypress 3 (Fig-l) for furtherrening where itis Amixed in withrthe-newchips being introduced to the press and proceedsithrough the sameprocess as has heretofore been described; The material passed by therotary screenas acceptable is collected and comprises the nished pulpofthe groundwood type.

The finished pulp, while beingof the groundwood type and equal theretoin quality, has nevetheless been produced from waste woodor wood ofinferior grades,` and has been produced with the expenditure' ofconsiderably less power than is normally required. Furthermore,.it

has been produced through the use of conventional equipment which may beVused and in fact'is-concurrently-being used for Ypurposes otherthanthe-production of groundwood type pulp.

Referring to Fig. 2 of 'the-drawing, this'ow diagramshows substantiallythe same process as has'heretoforebeen described exceptforthe omissionof'the'wetting or soaking vat 2. The process shown in Fig. 2 can beadvantageously utilized vin instances where the wood as it comes fromthe chipper has a reasonably high and uni-Y process of Fig. l involvingareve'rsal of the last twoV steps in said process as shownj in Fig. 1;In Fig. 3 the rotary screen 7 receives-the discharge from thes'econdstage rener 5 and grades thepulp byfseparation therefromofthe-long-'shives and' clustersV of unseparated-fibers priortothecleaning of thepulp. The'- material acceptedbyA the screen 7- is thenintroduced-into-the cleaner 6- for the removal of dirt, bark specks andthe like. The-material rejected by the screen 7 isreintroduced into theprocess forrefiningwhile the-material rejected by the cleaner 6isdirected-to the seweras--waste material.A This' modificationoftheprocess off-Fig. 1 -is advantageousz when using woods which arerelatively hard to fibrillate or separate into individual fibers. By useof the process of Fig. 3, the long shives and undefibered material areremoved prior to the cleaning of the pulp. This permits use of lesscleaning capacity inasmuch as the entire volume is not passing throughthe cleaner.

Depending upon the Vamount of re-refining required to separate the longshives and clusters of undefibered material rejected by the screen 7,such rejects may be reintroduced into the rotary press 3, as shown inFig. l, or reintroduced into the first refining stage or mill 4, asshown in Fig. 4. Where the amount of re-refining needed is notextensive, the modification of Fig.v 4 has been found quite successful.In this form of the process the rejects from the screen 7 are introducedinto mill 4 along with the material discharged from the rotary press 3and they then proceed through the process again. The reversal of thecleaner 6 and screen 7, as shown in Fig. 3, may also be made in themodification of Fig. 4. Such change in Fig. 4 would be made for the samereasons and would produce the same results as previously explained inconnection with Fig. 3.

Fig. 5 shows a further modification of the basic process of Fig. 1 whichmay be advantageously used in certain circumstances determined primarilyby the type of wood being used. In this modification, the screen orgrading member 7 is interposed between the first stage refining mill 4and the second stage refining mill 5. As previously noted, the `materialas it leaves the first stage mill 4 contains a certain quantity of shortfibers. If it is desirable to take precautionary measures to preventover-refining of the acceptable portion, the stock may be led directlyto the centrifugal cleaner 6. In so doing the second stage refiningAmill 5 is completely by-passed by the acceptable portion of the stockdischarged from refining mill4. To accomplish this the grading screen 7is interposed between the mills 4 and 5 with the long shives andclusters of unseparated fibers forming the rejects from the screen 7being introduced into the second refining mill 5 for further refiningaction. The acceptable portion from the screen 7 lay-passes the secondmill 5 and is introduced into the cleaner 6 simultaneously with theintroduction of the material thereto from the second refining mill 5.Thus, any danger of over-refining of the pulp material is obviated.

'I'he modification of Fig. 5 is well suited for use when treating woodswhich are easily separated or fibrillated.

In view of the foregoing it will be appreciated that there has beenevolved a completely new process for the production of groundwood typepulps utilizing machines which although conventional in design and wellknown for other purposes have never before been known or used for theproduction of groundwood type pulp. Thus, not only does the presentinvention include a new process for the production of groundwood typepulp but further includes a new result obtained through the use of oldmachines and a new product created thereby.

From the above description it will be apparent that there is thusprovided a device of the character described possessing the particularfeatures of advantage before enumerated as desirable, but whichobviously is susceptible of modification in its form, proportions,detail construction and arrangement of parts without departing from theprinciple involved4 or sacrificing any of its advantages.

While in order to comply with the statute the invention has beendescribed in language more or less specic 4as to structural features, itis to be understood that the invention is not limited to the specificfeatures shown, but that the means and construction herein disclosedcomprise but one of several modes of putting the invention into effect,and the invention is therefore claimed in any of its forms ormodifications Within the legitimate and valid scope of the appendedclaims.

Having thus described my invention, l claim:-

l. The method of producing groundwood pulp consisting of the steps ofchipping pulp wood, waste wood and the like, wetting and soaking saidchips, subjecting said soaked chips to alternate continuous applicationand release of mechanically applied pressure for a predetermined periodto effect a high degree of fiberization of said chips and extractsubstantially all the moisture and natural wood uids therefrom in asingle pass, introducing water to said chips ,upon final release ofpressure, subjecting said pressed chips with water added thereto to afurther fiberizing action in a disc mill, discharging said fiberizedchips into a centrifugal cleaner for the removal of impurities, dirtspecks and the like, the rejects from said cleaner being discharged towaste, subjecting the accepted portion of said stock to the action of arotary screen for removal of long shives and undefibered chips, thestock removed therefrom being :returned to the pressure stage of theprocess for further processing, the finally accepted material beingacceptable groundwood pulp.

2. The method as set forth in claim 1, characterized by the addition ofsodium hydroxide or its equivalent for the softening of lignin, sugarsand other compositions in the chips simultaneously with the wetting orsoaking of the chips.

3. The method of producing groundwood pulp comprising the steps ofchipping pulp wood, waste wood and the like, wetting and soaking saidchips, subjecting said soaked chips to continuous alternate applicationand release of mechanically applied pressure-for a predetermined periodto effect a 'high degree of fiberization of said chips and extractsubstantially all the moisture and natural wood fluids therefrom in asingle pass, introducing water to said chips upon nal release ofpressure, subjecting said pressed chips with water added thereto to afiberizing action in a disc mill, cleaning and separating said fiberizedchips by use of a centrifugal cleaner and a rotary screen, the materialretained after such cleaning being acceptable groundwood pulp, therejected material from said centrifugal cleaner being waste and therejected material from said rotary screen being reintroduced in theprocessing at the disc mill or prior thereto.

4. The method set forth in claim 3, characterized by a reversal of thecentrifugal cleaning and rotary screening steps, whereby the material asit comes from the disc mill is subjected rst to the rotary screen andthen to the centrifugal cleaner.

5. A process for producing groundwood pulp from raw uncooked Wood, woodwaste or the like, consisting of chipping the raw wood, introducing saidchips into a rotary mechanical press, subjecting said chips to a seriesof pressure applications, there being a complete release of pressureintermediate successive pressure applications, said treatment beingeffected during rotary movement of the chips through the press therebycausing a break down of chip structure and an opening up of the fibrousstructure of the chips, the natural wood iiuids and chemicals beingextracted from the chips during passage through the press, immediatelymoistening the fiberized chips as they are discharged from the press,adding additional water thereto and subjecting the moistened tiberizedchips with the additional water to a staged disc mill refiningoperation, and cleaning and grading the fibers after refining.

6. The process set forth in claim 5, characterized by a rotary screeningof the refined berized chips intermediate the stages of the refiningoperation, material rejected in the process being further refined andthe accepted material being directly introduced to Acleaning equipment.

7. The process set forth in claim 5, characterized by the rejects fromthe grading operation being returned to the beginning of the processingin the refining operation.

8. The process set forth in claim 5, characterized by the rejects fromthe grading operation being re-introduced into the mechanical press.

9. A continuous flow system for the making of groundwood pulpvconsisting 'ofa wood chipper, means operatively connected rthereto Yfor.wetting the chips made'by saidchipper, arotary screw type pressoperatively connected to-said chipper in following relation theretowherein the chips aresubjected to successive pressure increases anddecreases during rotary and longitudinal travel of the chips through the.pressrto produce a fibrous. material substantially free of liquid,means connected for adding water to the fibrous material as it isdischarged from the press, refining means operatively connected to thepress for acting upon said fibrous material in successive stages, avcleaner operatively connected to said refining means to which therefined fibrous material is discharged, and a grader connected forreceiving the acceptable material from the cleaner.

l0. A continuous iiow system for the making of groundwood pulpconsisting of a wood chipper, means for wetting the chips made by saidchipper connected therewith, a rotary screw type press connected toreceive the wetted chips and subject them to successive pressureincreases and decreases during concurrent rotary and longitudinal travelof the chips through the press to produce a fibrous material, meansconnected for adding water to the fibrous material as it is dischargedfrom the press, refining means `operatively connected to the press foracting upon said fibrous material in successive stages, means connectedfor cleaning and grading the fibrous material discharged from therefining means, and means connected with the last named means forre-introducing a portion of the graded fibrous material to the refiningmeans. Y

1l. A continuous flow process for producing groundwood pulp from'rawuncooked wood consisting of the steps of chipping the raw wood, wettingthe chips under conditions of substantially atmospheric pressure andtemperature, fiberizing the chips in a rotary screw type press bysuccessive applications and release of pressure during continuous`concurrent rotary and longitudinal traveltherethrough, refining-thefiberized materialgand finally grading and cleaning the refined berizedmaterial. '12. The process set forth in claim y11, characterized bytheaddition of water to the fiberized material prior to the refiningthereof, and the refiberation ofithe vmaterial rejected by the gradingoperation. n M

13. A method of producing groundwood pulp of..waste wood consistingofthe steps of chipping the wood, Wetting and soaking said chips,subjecting said .chips `to a simultaneous rotary and longitudinal flowwhile effecting a squeezing Aand shearing thereof in V'successivelintermittentffashion to extract the moisture Tand vother liquidsytherefrom and add a degree of ,heat theretosthereby, introducing waterYto the` partially fiberized chipsresultrefining the Vchips with Wateradded theretoxin :an attrition -mill to further fiberizesaid chipsto'naAdegree suitable for insulation V:board material, subjecting .saidfiberized material 'to a second stage rener berizingvaction to producepulp usable in newsprint, and subjecting the/product of the second stagerefner to aV centrifugal cleaning and rotary screening action to'providea. finished pulp having a high and uniform quality, Ythe/rejects beingreturned for further refining.

References-Cited in the tile of this patent UNITED STATES PATENTSAronovsky et val Y'May 10, 1955

1. THE METHOD OF PRODUCING GROUNDWOOD PULP CONSISTING OF THE STEPS OFCHIPPING PULP WOOD, WASTE WOOD AND THE LIKE, WETTING AND SOAKING SAIDCHIPS, SUBJECTING SAID SOAKED CHIPS TO ALTERNATE CONTINUOUS APPLICATIONAND RELEASE OF MECHANICALLY APPLIED PRESSURE FOR A PREDETERMINED PERIODTO EFFECT A HIGH DEGREE OF FIBERIZATION OF SAID CHIPS AND EXTRACTSUBSTANTIALLY ALL THE MOISTURE AND NATURAL WOOD FLUIDS THEREFROM IN ASINGLE PASS, INTRODUCING WATER TO SAID CHIPS UPON FINAL RELEASE OFPRESSURE, SUBJECTING SAID PRESSED CHIPS WITH WATER ADDED THERETO TO AFURTHER FIBERIZING ACTION IN A DISC MILL, DISCHARGING SAID FIBERIZEDACTION IN A DISC MILL, DISCHARGING MOVAL OF IMPURITIES, DIRT SPECKS ANDTHE LIKE, THE REJECTS FROM SAID CLEANER BEING DISCHARGED TO WASTE,SUBJECTING THE ACCEPTED PORTION OF SAID STOCK TO THE ACTION OF A ROTARYSCREEN FOR REMOVAL OF LONG SHIVES AND UNDEFIBERED CHIPS, THE STOCKREMOVED THEREFROM BEING RETURNED TO THE PRESSURE STAGE OF THE PROCESSFOR FURTHER PROCESSING, THE FINALLY ACCEPTED MATERIAL BEING ACCEPTABLEGROUNDWOOD PULP.